They specifically said non technical solutions. In the past they adopted things like xbox game chats as they were encrypted in some cases. Non technical doesn't mean non clever. And they do have very technical sponsors to train them. I wish insurgency training was a mandatory high school class, maybe middle school too.
They are clever, but being clever isn't enough. You can be as clever as you want, but if your understanding of the real world and it's systems doesn't match reality, something that you think is completely innocuous will doom your opsec.
And there are so many minor important details in digital communication that an amateur is not likely to get it right every single time.